2-Hydroxy-1-naphthaldehyde-N-methylethanesulfonylhydrazone was synthesized and its structure was investigated by X-ray diffraction. IR, NMR and mass spectroscopies. it crystallizes in the monoclinic system, space group P2(1)/c, a = 22.712(4), b = 5.793(4). c = 11.032(2) angstrom, alpha = 90.0, beta = 102.070(8)degrees, gamma = 90.0 degrees, V = 1419.4(1) angstrom(3), Z = 4. Spectroscopic assignment and calculations carried out using B3LYP/6-31G** basis set and crystallographic results indicate the predominance of the phenol-imine tautomeric form. It has strong intramolecular hydrogen bond of type O-H N [with distance donor-acceptor 2.579(4) angstrom]. The angular disposition of the bonds about the sulfur atom significantly deviates from that of a regular tetrahedron as expected. This deviation can be attributed to the non-bonded interactions involving the S=O bonds and methyl groups in both molecular and crystal structure. Result of conformational analysis was also compared with crystallographic data. Antimicrobial activity of the title compound was screened against E. coli ATCC 11230, P. aeruginosa ATCC 28753, S. enterititis ATCC 40376, S. aureus ATCC 25923 and B. cereus RSKK 863. (c) 2008 Elsevier B.V. All rights reserved.